Presently on UHF band, but starting next year, the band from Channel 7 up through UHF -- though ch 52-69 will eventually be reallocated to something besides TV. (if this is wrong, please correct me). And I HIGHLY recommend a rooftop antenna if possible. I use a regular Home Depot TV antenna mounted to my chimney running on RG6 75-ohm coax cable and easily recieve all the So Cal HD over-the-air channels. I watched the Celtics in HD on Channel 7-1 today...

".......Are DTV signals broadcast on special frequencies?

No. DTV broadcasts use exactly the same channels as regular analog television. While many DTV stations are now occupying UHF broadcast channels, broadcasters are allowed to move back to their original VHF or UHF TV channel once the transition to DTV is complete.

The only caveat is that TV channels 51 through 69 will be auctioned off for other uses at the end of the transition to digital TV. Stations who originally had analog channels in this band will have to move, no matter what...............Tests so far seem to indicate that high VHF channels (7-13) are quite well suited for DTV broadcasts, and many broadcasters plan to move back to their high VHF channels at the end of the transition. VHF transmitters also cost much less money to operate than UHF transmitters....."

previous quote from here: http://www.avsforum.com/hdtvfaq/HDTV...%20television?

See here also:
http://www.solidsignal.com/antennas/antenna_faqs.asp